Surface display device with a non-rectangular display surface shape and electronic device including same

ABSTRACT

Disclosed is a display device for use of a surface display of an arbitrary shape, including a plural number of display element units, each made up of a circuit that forms a single stage of a scanning circuit and a pixel circuit connected to an output of the scanning circuit, are arranged in a unicursal fashion on a display substrate.

REFERENCE TO RELATED APPLICATION

The present application is claiming the priority of the earlier Japanesepatent application No. 2006-280234 filed on Oct. 13, 2006, the entiredisclosure thereof being incorporated herein by reference thereto.

FIELD OF THE INVENTION

This invention relates to a display device. More particularly, thisinvention relates to a surface display device, such as a liquid crystaldisplay or an EL (electoluminescence) display, being able to have adisplay surface shape other than a rectangular surface shape.

BACKGROUND OF THE INVENTION

In an active matrix liquid crystal display device, a plurality of pixelsare arranged in rows and columns, that is, in a matrix array. Each rowof the matrix of pixels shares a gate wiring connected to the gateelectrodes of thin-film transistors (TFTs). Each column of the matrix ofpixels shares a data wiring supplied with a data signal. The signal onthe gate wiring on/off controls the thin-film transistors, such that,when the thin-film transistors are on, the signal on the data wiring issupplied to the liquid crystal material to modify the opticalcharacteristic of the liquid crystal material.

FIG. 19 shows a typical pixel configuration in an active matrix liquidcrystal device. Each row of a pixel matrix shares a common gate wiring10, whereas each column of the pixel matrix shares a common data wiring12. Each pixel includes a thin-film transistor 14 and a liquid crystalcell 16, arranged in series between the data wiring and a commonelectrode 18. The thin-film transistor 14 is turned on or off by asignal supplied to the gate wiring. Hence, the gate wiring is connectedto the gate electrodes of the thin-film transistors 14 of the rowassociated with the pixel in question. Each pixel includes a storagecapacitor 20. This storage capacitor 20 has its one end connected to thenext gate wiring, previous gate wiring or to a further wiring forstorage capacitor. The storage capacitor 20 stores electric charge toretain the voltage at the liquid crystal cell 16 even after thethin-film transistor 14 is turned off.

To apply desired voltage to a liquid crystal cell to acquire the neededgrayscale level, a relevant signal is supplied to the data wiring insynchronization with an address signal on the gate wiring. This addresssignal turns on the thin-film transistor 14, therebycharging/discharging the liquid crystal cell to desired voltage andsimultaneously charging/discharging the storage capacitor in keepingwith the signal charge applied to the data wiring.

An address signal turns the thin-film transistor 14 off. The storagecapacitor 20 retains the voltage across both ends of the liquid crystalcell 16 during addressing of other rows. The storage capacitor 20reduces variations in the liquid crystal cell voltage due to leakageduring the off-time of the thin-film transistor 14, capacitive couplingor to variations in the dielectric constant of the liquid crystal.

Each row is addressed in succession so that all rows will be addressedduring one frame period.

FIG. 20 is a plan view showing the configuration of a typical activematrix liquid crystal display device. In FIG. 20, the address signal issupplied by a gate driver circuit 30, whilst the data signal is suppliedto a pixel matrix 34 by a data driver circuit 32. FIG. 20 shows arectangular active matrix liquid crystal display device.

Patent Document 1 discloses a non-rectangular display device. FIG. 21depicts a plan view of a non-rectangular display disclosed in thisPatent Document.

The display device of this Patent Document 1 includes an array ofpixels, a gate driver circuit part, indicated by R, and a data drivercircuit part, indicated by C. Each pixel is addressed by the gate drivercircuit and the data driver circuit part, connected to a related rowwiring and to a related column wiring, with the array of pixels being ofa non-rectangular configuration. The display device also includes atleast three of the aforementioned gate driver circuit parts and at leastthree of the aforementioned data driver circuit parts, arranged alongthe outer rim of the array. These gate driver circuit parts and datadriver circuit parts are alternately arranged along the outer rim of thearray of pixels. These gate driver circuit parts and data driver circuitparts may be formed on the same substrate as that on which the pixels ofthe display device are arranged. For example, the pixels and the drivercircuit parts may be fabricated using the polysilicon process technique.

[Patent Document 1] JP Patent Kohyo Publication No. JP-P2005-528644A

SUMMARY OF THE DISCLOSURE

The entire disclosure of the above mentioned Patent Document is hereinincorporated by reference thereto. The following analysis is given bythe present invention.

The above-described conventional display device has the followingproblems.

The first problem is that the conventional display device cannot affordan arbitrary shape. That is, the conventional technique allowsfabrication of display devices of only a limited range of thenon-rectangular shape, but suffers from a highly limited degree offreedom of shape designing.

One of the reasons is that the driver circuit units are arranged forextending along the outer periphery of the matrix of pixels. Theconventional technique is in need of a transversely extending gatewiring and a vertically extending data wiring in order to address apixel. The gate wiring and the data wiring are provided for extendingfrom each pixel up to the outer periphery of the pixel matrix. Since itis necessary to prevent the gate and data wirings from beinginterrupted, there are placed limitations on the degree of freedom inthe shape of the display device. Depending on the shape of the displaydevice, there is raised a problem that the wirings are partiallyinterrupted such that there may be a non-addressable pixel area in thedisplay device.

Another reason the display device of the conventional technique cannotcope with an arbitrary shape is that a driver circuit of a TAB (TapeAutomated Bonding) configuration is connected to the outer rim of thepixel matrix part. The TAB is handled in the configuration of afilm-shaped TCP (Tape Support. Package). Before being severed intoindividual TAB pieces, the TAB is wrapped as a coil around a drum like amotion picture film.

Hence, the as-severed TAB is flat and is usually connected to a liquidcrystal panel using an anisotropic electrically conductive film on aliquid crystal panel before being bent.

If, after connecting the TAB to a liquid crystal panel having acurvilinear outer profile, the TAB is to be bent in the heart shape as adesign feature, as shown in FIG. 21, this bending represents a difficultoperation.

The reason is that the TAB bend is usually rectilinear in shape.

This problem is felt more keenly as the radius of curvature of the outerprofile becomes smaller. In addition, if there are a plural number ofcrests and recesses in a sole TAB connection, it is extremely difficultto bend the TAB along this shape to provide the design feature.

The second problem is that mask designing is extremely time-consuming ifthe driver circuit unit is to be formed along the curvilinear shape ofthe outer profile with the use of the polysilicon process technique.

Like the layout of a pixel matrix part, the layout of the driver circuitof the display device is drawn by arranging a plural number of unitcells in the form of an array.

In the case of a gate driver circuit, a unit cell, made up of a circuitconstituting a single stage of a scanning circuit, a circuit forbuffering an output of the single stage of the scanning circuit and acircuit for enabling an output of the single stage, is prepared. Thepitch and the number of the unit cells are specified on CAD (ComputerAided Design), whereby the cells are arrayed on a straight line toenable a desired circuit layout to be obtained in a short time.

Although the current CAD for circuit layout has the function of linearlyarraying the unit cells in the X- and Y-directions, it does not have thefunction of arraying the unit cells along a curve.

That is, to prepare a layout of driver circuit units along the outer rimof a display device, it is necessary to arrange the unit cells one byone by a manual operation, or to prepare a number of arrays, each madeup of several unit cells, and to arrange the so prepared arrays, againby a manual operation. Hence, the mask designing is an extremelytime-consuming operation and a mask designer has to go home as he/shehas been fatigued with the laborious operation.

It is therefore an object of the present invention to enhance the degreeof freedom in designing the shape of a display device and to provide adisplay device of an arbitrary shape.

It is another object of the present invention to achieve shorterdesigning time for a display device of an arbitrary shape and to providea display device having improved productivity.

It is a further object of the present invention to provide a displaydevice whereby it is possible to narrow down the frame width/length ofthe display device as the above objects are fulfilled.

It is a further object of the present invention to provide a displaydevice whereby it is possible to reduce the number of connectionterminals of a substrate of a display device as the above objects arefulfilled.

It is yet another object of the present invention to provide a displaydevice whereby it is possible to elevate the aperture ratio of pixels asthe above objects are fulfilled.

The present invention has substantially the following configuration.Meanwhile, in the following description, the reference numerals in thedrawing are appended in parentheses to specify the components. This,however, is intended to help comprehend the present invention and shouldnot be interpreted to restrict the scope of the invention.

In one aspect, the present invention provides a surface display devicecomprising a plurality of display element units arranged with one strokeon a display substrate. Each of the display element units includes acircuit constituting a single stage of a scanning circuit (also termed a‘unit circuit’ of the scanning circuit) (206 of FIG. 2) and a pixelcircuit (202) connected to an output node (n2 of FIG. 2) of the unitcircuit. That is, a plurality of display element units (200), eachcomposed of a circuit (206 of FIG. 2), forming a single stage of thescanning circuit, and a pixel circuit (202), connected to an output node(n2 of FIG. 2) of the circuit (206 of FIG. 2), are arrayed in successionon a display substrate (208 of FIG. 1).

The scanning circuit is preferably driven by a clock signal which is asingle-phase clock signal.

In another aspect, the present invention provides a surface displaydevice comprising a scanning circuit (204) including a transistor(214(a), 214(b), 214(c), . . . of FIG. 13) for outputting the scanningsignal to the output node of the scanning circuit and a pixel circuit(202) connected to the output node, wherein the transistor outputtingthe scanning signal to the output node and the sole pixel circuit arearranged as a set and a plurality of the sets of the transistors and thepixel circuits are arrayed together to form substantially the entirearea of a display area.

In a further aspect, the present invention provides a surface displaydevice comprising a scanning circuit (204) including a transistor(214(a), 214(b), 214(c), 214(d) . . . of FIG. 13) for outputting thescanning signal to the output node of the scanning circuit, and a pixelcircuit (202) connected to the output node, wherein the transistoroutputting the scanning signal to the output node and the sole pixelcircuit are arranged as a set and a plurality of the sets of thetransistors and the pixel circuits are arrayed together on the surfacedisplay device to constitute the display area. The transistors used inthe scanning circuit and in the pixel circuits are polysilicon TFTsformed on a glass substrate.

In a further aspect, the present invention provides a surface displaydevice comprising the scanning circuit arranged with one stroke orunicursally on a non-rectangular display substrate and a pixel circuitconnected to each output stage of the scanning circuit. The scanningcircuit is arranged on the display substrate (208) as it presents atleast one folded part (52), whereby the non-rectangular display area isformed.

In a further aspect of the present invention, the present inventionprovides a surface display device comprising the scanning circuitarranged with one stroke or unicursally on the display substrate and apixel circuit connected to each output stage of the scanning circuit.The scanning circuit is arranged spirally on the display substrate torender it possible to form a non-rectangular display area (FIG. 5).

In a further aspect, the present invention provides a surface displaydevice comprising a plurality of pixel circuits (202) and a scanningcircuit (204) for sequentially applying a voltage to the pixel circuits.A part of the scanning circuit is arranged between neighboring ones ofthe pixel circuits or underneath the pixel circuit.

In a further aspect, the present invention provides a surface displaydevice wherein a circuit including a plurality of pixel circuits (202)and a scanning circuit (204) for sequentially applying the voltage tothe pixel circuits is arranged on a display substrate so as to have atleast one bend (FIG. 1).

In a further aspect, the present invention provides a surface displaydevice wherein a spiral array of a plurality of pixel circuits (202) anda scanning circuit (204) for sequentially applying the voltage to thepixel circuits is spirally arranged on a display substrate (FIG. 5).

In a further aspect, the present invention provides a surface displaydevice wherein a flexible linear display unit (302) made up of ascanning circuit and a plurality of pixel circuits that may be selectedby the scanning circuit is wrapped at least two turns on a support (304)(FIGS. 7A to 7B).

In a further aspect, the present invention provides a display device inwhich a transistor constituting a pixel switch (350) has a gateelectrode connected to an output node of a scanning circuit, whereinoutput nodes (n1, n3, n5, . . . of FIG. 13) of odd stage unit circuitsof the scanning circuit output a scanning signal of a first polarity(active-low), and output nodes of even stage unit circuits (n2, n4, n6,. . . of FIG. 13) of the scanning circuit output a scanning signal of apolarity opposite to the first polarity. The pixel switches connected tothe output nodes of odd stage unit circuits of the scanning circuit areeach a transistor of a first conductivity type (p-type), whereas thepixel switches connected to the output nodes of even stage unit circuitsof the scanning circuit are each a transistor of a second conductivitytype (n-type).

In a further aspect, the present invention provides a display devicewherein the odd stage unit circuits of the scanning circuit each includean inverter circuit (54 of FIG. 13) receiving a pulse signal from aprevious stage, and switching transistors (214 a, 214 c of FIG. 13) of asecond conductivity type (n-type) connected between an output node ofthe inverter circuit and an output node of the scanning circuit. Theeven stage unit circuits of the scanning circuit each include aninverter circuit receiving a pulse signal from a previous stage andswitching transistors (214 b, 214 d of FIG. 13) of a first conductivitytype (p-type) connected between the output node of the inverter circuitand the output node of the scanning circuit. A common clock signal isapplied to each of the gate electrodes of the switching transistors.

In a further aspect, the present invention provides a display devicewherein the odd stage unit circuits and the even stage unit circuits ofthe scanning circuit each include a clocked inverter (56 of FIG. 15A)receiving a pulse signal supplied from a previous stage. The output nodeof the clocked inverter is an output node of the scanning circuit. Aclock signal is supplied to the gate electrode of the transistor of thesecond conductivity type (n-type) of the clocked inverter in the oddstage unit circuit of the scanning circuit. A signal obtained byinverting the clock signal is supplied to the gate electrode of thetransistor of the first conductivity type (p-type) of the clockedinverter. A signal obtained by inverting the clock signal is supplied tothe gate electrode of the transistor of the second conductivity type(n-type) of the clocked inverter in the even stage unit circuit of thescanning circuit. The clock signal is supplied to the gate electrode ofthe transistor of the first conductivity type (p-type) of the clockedinverter (FIGS. 15A and 15B).

In a further aspect, the present invention provides a display devicewherein each of the odd stage unit circuits and each of the even stageunit circuits of the scanning circuit each include an inverter circuit(54 of FIG. 15B) receiving a pulse signal from a previous stage, and aCMOS transmission gate (58) connected between an output node of theinverter circuit and an output node of the unit circuit. A clock signalis supplied to a gate electrode of a transistor of a second conductivitytype (n-type) of the CMOS transmission gate in the odd stage unitcircuit of the scanning circuit. A signal obtained by inverting theclock signal is supplied to the gate electrode of the transistor of thefirst conductivity type (p-type) of the CMOS transmission gate. Thesignal obtained by inverting the clock signal is supplied to the gateelectrode of the transistor of the second conductivity type (n-type) ofthe CMOS transmission gate in the even stage unit circuit of thescanning circuit. The clock signal is supplied to the gate electrode ofthe transistor of the first conductivity type (p-type) of the CMOStransmission gate.

In a further aspect, the present invention provides a display devicewherein each of the even stage unit circuits and each the odd stage unitcircuits of the scanning circuit each include a single-phase clockcontrolled inverter (60) comprising:

first to fourth switch devices (M01 to M04 of FIG. 17B), sequentiallyconnected in series between a high potential side power supply and a lowpotential side power supply; wherein

said first and second switch devices are each a p-type MOS transistor;and

said third and fourth switch devices are each an n-type MOS transistor;

gate electrodes of one of said p-type MOS transistors (M02) and one ofsaid n-type MOS transistors (M03) being connected in common andreceiving a pulse signal supplied from a previous stage; while a clocksignal is supplied to the gates of the remaining two MOS transistors(M01, M04);

drain electrodes of said one of said p-type MOS transistors (M02) andsaid one of said n-type MOS transistors (M03) being connected in commonto constitute the output node of the unit circuit.

The meritorious effects of the present invention are summarized asfollows.

The first meritorious effect of the present invention is that a displaydevice of an arbitrary shape may be implemented.

One of the reasons is that a plural number of display element units,each composed of a circuit forming a single stage of the scanningcircuit, and a pixel circuit, connected to an output node of thescanning circuit, are connected in cascade so that all pixels will beaddressed sequentially. The resulting circuit is arranged in a unicursalfashion on a display substrate to form a display area. That is, theunicursally arranged array may optionally be laid out to form a displayarea of an arbitrary shape.

Another reason is that, since the display element units are arrayed withone stroke or unicursally on the display substrate to form a displayarea, it is possible to address all pixels in the display area. In aconventional display device, the pixels arranged at the points ofintersection of data wirings linearly arranged in the vertical directionand gate wirings linearly arranged in the horizontal direction areaddressed. Thus, depending on the shape of the display device, there israised a problem that certain pixel areas may be non-addressable due towiring disconnection.

Still another reason is that, since the display area of the displaysubstrate is constituted by unicursally arranged display element units,it is sufficient that a connection part between the display substrateand the circuit for driving the display substrate is located at an endof the unicursally arranged display element units. Hence, the number ofthe connection terminals for connection with the circuit driving thedisplay substrate may be reduced, so that there is no necessity ofproviding the drivers of the TAB type on the outer rim of the displayarea, or the number of the drivers may be reduced. The bend parts of theTAB are usually linear so that it has been extremely difficult toprovide a curved shape of the outer rim of the display substrate.

The second meritorious effect of the present invention is that maskdesigning time may be reduced.

The reason is that there is no necessity of laying out the drivercircuit along the curved outer shape of the outer rim. In implementingthe present invention, a number of sets of laid-out display elementunits, with each set being a unit cell, are arrayed along the transversewidth of the display area to complete a layout for each row. Thisprocess is the same as that of arraying one row of pixels in theconventional process. Heretofore, the driver circuits need to be laidout non-linearly along the outer rim. This operation may be dispensedwith and hence the mask designing time may be reduced.

The third meritorious effect of the present invention is that the framewidth of the display device may be decreased.

The reason is that there is no necessity of providing the driver circuitalong the outer rim of the display substrate. That is, the displayelement units may be arranged up to the outer rim of the displaysubstrate so that the shape of the display substrate will be coincidentwith the shape of the display area, as a result of which the framewidth/length of the display device may be decreased.

The fourth meritorious effect of the present invention is that thenumber of connection terminals of the display substrate may be reduced.

The reason is that, since the display area on the display substrate isconstituted by the unicursally arranged display element units, the sitesof connection between the display substrate and the circuit for drivingthe substrate is located at one end of the unicursally arranged displayelement units.

The fifth meritorious effect of the present invention is that theaperture ratio of the pixels may be increased.

The reason is that the number of the transistors that make up thescanning circuit and the number of the clock signals driving thescanning circuit are only small.

Still other features and advantages of the present invention will becomereadily apparent to those skilled in this art from the followingdetailed description in conjunction with the accompanying drawingswherein examples of the invention are shown and described, simply by wayof illustration of the mode contemplated of carrying out this invention.As will be realized, the invention is capable of other and differentexamples, and its several details are capable of modifications invarious obvious respects, all without departing from the invention.Accordingly, the drawing and description are to be regarded asillustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is plan view showing a surface display device of an example ofthe present invention.

FIG. 2 is a circuit diagram showing the surface display device of anexample of the present invention.

FIG. 3 is a plan view showing another surface display device of anexample of the present invention.

FIG. 4 is a plan view showing still another surface display device of anexample of the present invention.

FIG. 5 is a plan view showing still another surface display device of anexample of the present invention.

FIG. 6 is a plan view showing still another surface display deviceaccording to the present invention.

FIGS. 7A and 7B are a perspective view and a circuit diagram of afurther surface display device of an example of the present invention,respectively.

FIG. 8 is a circuit diagram of a display device of an example of thepresent invention.

FIG. 9 is a detailed circuit diagram of an example of the presentinvention.

FIGS. 10A, 10B and 10C are circuit diagrams of a DFF of an example ofthe present invention.

FIGS. 11A and 11B are a detailed circuit diagram showing an example ofthe present invention and a circuit diagram of symbols, respectively.

FIG. 12 is a detailed circuit diagram showing an example of the presentinvention.

FIG. 13 is a circuit diagram showing an example of the presentinvention.

FIG. 14 is a timing chart showing the operation of the circuit shown inFIG. 13.

FIGS. 15A and 15B are a circuit diagram showing an example of thepresent invention and a circuit diagram showing a modification thereof,respectively.

FIG. 16 is a timing chart showing the operation of the circuit shown inFIGS. 15A and 15B.

FIGS. 17A, 17B and 17C are a circuit diagram showing an example of thepresent invention, a circuit diagram of a single-phase clock controlledinverter and a truth table, respectively.

FIG. 18 is a timing chart showing the operation of the circuit shown inFIGS. 17A to 17C.

FIG. 19 is a diagram for a pixel of a typical active matrix liquidcrystal display device.

FIG. 20 is a plan view showing a typical active matrix liquid crystaldisplay device.

FIG. 21 is a plan view showing a non-rectangular display devicedisclosed in the patent document 1.

PREFERRED MODES OF THE INVENTION

With reference to the accompanying drawings, preferred examples of thepresent invention will be described in detail.

Example 1

FIG. 1 shows the configuration of an active matrix liquid crystaldisplay device as an example of the present invention, in the exampleshown in FIG. 1, a large number of display element units are arrangedwith one stroke or unicursally within a display area substantiallycoincident with the shape of a display substrate (208) to constitute asurface display device. That is, the display element units are arrangedwith one stroke or unicursally as they are bent at more than one site toconform to the shape of the display area to constitute a surface displaydevice.

The display element units and an array of the display element units arenow described with reference to FIG. 2. By the array of the displayelement units is meant an array of the display element units on thedisplay substrate.

Referring to FIG. 2, the display element unit (200) is made up of acircuit (206) that forms a stage of a scanning circuit, also termed a‘unit circuit’ of the scanning circuit, and a pixel circuit (202)connected to an output node of the circuit (206).

More specifically, the circuit (206), forming a stage of the scanningcircuit, is e.g., a D-type flip-flop, abbreviated to DFF, and a pixelcircuit is connected to an output node Q of the DFF. The DFF samples aninput signal supplied to an input node D to output sampled signal at anoutput node Q in synchronization with rise of a clock signal supplied toa CLK node.

The pixel circuit (202) includes: a pixel switch (350), the drainterminal of which is connected to a DATA node; a liquid crystal cell(16) connected between a source terminal of the pixel switch (350); anda common electrode VC (18), and a storage capacitor (20).

The storage capacitor (20) has one end connected to a node of the liquidcrystal cell (16) opposite to the common electrode VC (18). The oppositeend VA (22) of the storage capacitor (20) is connected to a wiring ofthe storage capacitor or to a wiring at a preset potential, such aspower supply wiring of the DFF.

By the unicursal array of the display element units (212 of FIG. 1) ismeant a circuit composed of cascaded connection of display element unitsin which output nodes Q of the DFFs of the display element units areconnected to input nodes D of the next-stage DFFs.

Meanwhile, a circuit composed of a plural number of the cascadedconnections, in which the output nodes of the DFFs of the displayelement units are connected to the input nodes D of the next-stage DFFs,is termed a ‘scanning circuit’ or a ‘shift register circuit’.

By a wiring that connects the output node Q of the DFF and the inputnode D of the next stage DFF, a pulse signal is transferred to thedownstream side stage in synchronism with the clock signal. The wiringthat connects the output node Q of the DFF and the input node D istermed a ‘pulse transfer wiring’ (300).

The scanning circuit and the pixel circuit are laid out on the displaysubstrate, using e.g., the polysilicon process technique, as shown inFIG. 3.

The scanning circuit (204) and the pixel circuits (202), which areconnected to the output node of the scanning circuit, are formed on thedisplay substrate, as shown in FIG. 3. The scanning circuit (204) andthe pixel circuits (202), connected to the output nodes of the scanningcircuit, make up a single row. A plural number of these rows make up adisplay area.

The pulse transfer wiring (300) is arranged to connect two neighboringrows. The connect portion is a folded part of the scanning circuit, laidout with one stroke or in a unicursal fashion, and is labeled a foldedpart (52) in FIG. 3.

A signal is supplied at an input terminal (210) provided at an end ofthe scanning circuit.

The scanning circuit is laid out so that the pitch of pixels, formed bythe pixel circuit, is constant in both the vertical and horizontaldirections.

By so doing, it is possible to avoid the feared problem of unneededlines produced on a display part to detract appreciably from the picturequality.

By adjusting the number of display element units that make up a row,adjusting the transverse length of each row in keeping with the displayarea, and by laying out plural rows, to fill up the display area, it ispossible to realize a display device of an optional outer shape.

Since the pulse transfer wiring (300) is arranged between neighboringrows, the scanning circuits in the respective rows may be arranged inthe entire display area with one stroke or in a unicursal fashion, andthe respective pixels are addressed in a unicursal fashion.

The operation of the present example is now described.

To apply a desired voltage to the respective liquid crystal cells toobtain the desired grayscale level, a proper signal is supplied to adata wiring connected to the DATA node in synchronization with an outputof the scanning circuit (204). An output signal of the scanning circuitturns on the pixel switch (350). This charges discharges the liquidcrystal cell (16) to a desired voltage, responsive to a signal voltageapplied to the data wiring, while simultaneously charging/dischargingthe storage capacitor 20.

The pixel switch (350) is then turned off by the output signal of thescanning circuit. The voltage written in the liquid crystal cell (16) ismaintained during addressing of the other pixel.

The scanning circuit outputs scanning signals in succession so that allpixels will be addressed in one frame period.

With the present example, the display element units (200) are arrangedin a display area of the display device, in a unicursal fashion, so thatit is possible to cope with display devices of optional shapes. Thiswill become clear by referring to other examples which will be describedsubsequently.

If, in the conventional display device, the pixels are to be addressed,it is necessary to provide gate wirings transversely extending to theouter rim of the display substrate and data wirings vertically extendingto the outer rim of the display substrate, thus imposing restrictions onthe degree of freedom in shape designing.

With the present example, the display area on the display substrate ismade up of the display element units arranged in a unicursal fashion. Itis therefore sufficient that the connection part between the displaysubstrate and the circuitry for driving the display substrate is at anend of the display element units, arranged in a unicursal fashion.Hence, there may be derived a meritorious effect that the number ofconnection terminals between the display substrate and the circuitry fordriving it may be reduced.

Thus, even though the substrate is flexible, due to use of the TAB forconnection, the sites of connection are limited to only a part of theouter rim of the display substrate. Hence, the design effect that theshape of the display area itself may be the shape of the display devicemay be achieved.

With the present example, the display area on the display substrate isconstituted by the display element units, arranged in the unicursalfashion, while it is sufficient that the connection part of the displaysubstrate for connection with the circuitry that drives the substrate isat one end of the unicursally arranged display element units. Thus, ifthe display area is of a pinched-in shape, such as gourd-shaped, and thepinched-in area is of an extremely narrow width, so that it is possibleto realize such shape of the display device, provided that the displayarea is of a width sufficient to accommodate the display element units.Stated differently, it is possible to cope with optional shapes of thedisplay devices.

With the present example, it is unnecessary to lay out the drivercircuit units along the curved outer rim, thus shortening the maskdesigning time.

In the present example, the display element unit is laid out toconstitute a unit cell, and a number of the unit cells, corresponding tothe transverse width of the display area, are arrayed in a line tocomplete the layout for one row. This process is the same as theconventional layout process for one row. Hitherto, the driver circuitunits need to be laid out non-linearly for extending along the outerrim. With the present example, this non-linear layout of the drivercircuit units along the outer rim may be dispensed with, thus enablingthe mask designing time to be reduced.

Meanwhile, if part or all of the display area is rectangular-shaped,row-based layout is not mandatory. In such case, the display area layoutmay be realized by arraying unit cells in a matrix and by adding ordeleting a unit cell or unit cells as necessary.

With the present example, the effect of narrowing down the framewidth/length of the display device may be derived. It is assumed in thefollowing that the driver circuit units of the display device are formedon the display substrate, using the polysilicon process technique, forinstance.

In case the driver circuit units of the display device of the relatedart, shown in FIG. 21, are formed on the display substrate, those drivercircuit units are laid out along the outer rim of the display substrate.Hence, the display area is on an inner side of the edge of the outer rimof the display substrate, and on an inner side of the layout area of thedriver circuit units arranged on the inner side of the outer rim edge.

Conversely, with the present example, it is unnecessary to lay out thedriver circuit units along the outer rim of the display substrate. It istherefore possible to arrange the display area to the very edge of thedisplay substrate.

Meanwhile, the driver circuit unit of the related art has to drive anumber of transistors equal to the number of transversely arrangedpixels and the parasitic capacitance of the transversely extending gatewirings. Hence, a buffer circuit composed of a large size transistor isneeded for the gate driver.

Conversely, with the present example, only one transistor (pixel switch)is connected to the output node of the circuit (206) that constituteseach stage of the scanning circuit. Moreover, the wiring connected tothis output node is of shorter length and has only small parasiticcapacitance, and hence there is no necessity of providing a buffercircuit constituted by a transistor of a larger size.

Example 2

In the above-described, example 1, the display element units arearranged in the entire display area in a unicursal fashion, as describedabove with reference to FIG. 1.

In an example 2, shown in FIG. 4, the display area is divided in pluralsub-areas, in each of which the display element units are arranged in aunicursal fashion.

In FIG. 4, there are eight sub-areas, of which only two are labeled 62 aand 62 b.

In the present example, in which the display area is divided into pluralsub-areas, it is possible to reduce the clock frequency afforded to thescanning circuit and the load capacitance of the clock signal wiring,resulting in the decreased clock delay.

Further, the load capacitance of the data wiring is decreased, resultingin the reduced delay of the data signal.

Thus, a display device of a larger size or a display device with alarger number of pixels may be driven more easily than with the example1.

In FIG. 4, input terminals (210 a˜210 h) are provided in the respectivesub-areas. Alternatively, a wiring may be provided on the displaysubstrate and the input terminals may be assembled together in one area.By so doing, the electrical connection to outside may be made bypackaging the flexible substrate in one location. This is desirable forfabrication of a display device of an arbitrary shape.

Example 3

In the above-described example 1, a plural number of rows, eachincluding a linear array of display element units, are arrayed side byside to constitute a display device, as described with reference toFIGS. 1 and 3. In an example 3 of the present invention, display elementunits are arranged spirally to constitute a surface display device.

Example 4

FIG. 6 shows the configuration of an example 4 of the present invention.The present example 4 refers to a surface display device, a displaysubstrate of which includes an aperture 50. With this shape of thedisplay device, the display area may be filled up with the unicursallyarranged display electrical element units. The degree of designingfreedom with respect to the shape of the surface display device is high.Moreover, since there is no necessity of providing driver circuit unitsalong the rim of the aperture formed in the display substrate, thedegree of freedom of the outer shape of the display device is also high.

This shape of the display device is difficult to implement with therelated art for the following reasons.

One of the reasons is that, since there is provided the aperture, thedata wiring or the gate wiring is interrupted, such that there may be anarea in which the wiring cannot be connected, or cannot be connectedwith ease, to the gate driver circuit or the data driver circuitarranged on the outer rim of the pixel matrix.

As a solution to this problem, it may be contemplated to additionallyprovide a data driver circuit or a gate driver circuit along the edge ofthe aperture.

An example of the method for providing the data driver circuit or thegate driver circuit is packaging by TAB. A set of terminals on theoutput side of the TAB is connected to a data line of a liquid crystalpanel or to an input terminal of a gate line using an anisotropicelectrically conductive film.

If the shape of the aperture is to be a design feature, and such effectis desired, the TAB needs to be folded to the back side of the displaydevice.

However, the aperture usually has a small radius of curvature, so thatit is difficult to fold back the TAB this way.

Further, designing restrictions, such as increased number of componentparts or increased cost, are newly presented, such as providingadditional wirings to be connected to the set of terminals on the TABinput side on the back surface of the display device.

Among other packaging methods, there is a method of forming a datadriver circuit or a gate driver circuit along the edge of the outer rimor the aperture, using the polysilicon process technique. A connectionterminal for signal input may be provided on a part of the edge of theouter rim.

However, in this case, it is necessary to provide a wiring to apply aninput signal to the driver circuit unit along the edge of the aperture.

If the polysilicon process technique is used, this wiring is formed onthe same surface as the surface carrying the pixel transistor. In thiscase, there may be produced such an area in which the layout of thepixel matrix part is out of order.

The result is that unneeded lines tend to be produced on a pixel matrixpart, that is, on a display area, to detract appreciably from the imagequality.

For these reasons, it is difficult to achieve the shape having theaperture shown in FIG. 6. This problem has now been overcome inaccordance with the present invention.

FIGS. 7A and 7B show the configuration of an example 5 of the presentinvention. Referring to FIGS. 7A and 7B, the present example will now bedescribed. In the present example, a scanning circuit (204) and a pixelcircuit (202), which is connected to each output node of the scanningcircuit (204), are formed on an elongated flexible substrate. Thiselongated display device, that is, a line-shaped display device (302),is wrapped around a support (304) to provide a surface display device.

With the present example, the display area of the display device isconstituted by unicursally arranged display element units (200). It istherefore sufficient if the connection part between the display deviceand the circuitry for driving the display device is located at an end ofthe unicursally arranged display element units, with the result that thenumber of connection terminals between the display device and thecircuitry for driving the display device may be reduced.

Other Examples

In the above-described examples, an example of an active matrix liquidcrystal display device is shown. However, the configuration of thedisplay device is not limited to this example. For example, the displaydevice may be a surface display device constituted by pixels, such as anEL (Electroluminescence) display device, electronic paper or anelectrical field emission type display device, for which case themultiple favorable effects such as stated in the above examples may bederived.

In the above-described examples, such a configuration in which displayelement units are formed on a display substrate using the polysiliconprocess technique is shown as the configuration of forming the displayelement units on display substrate. The present invention may, ofcourse, not be limited to this fabrication method. For example, theamorphous silicon process technique or a variety of organic semiwiringprocess techniques may be used for forming the display element units.Or, a single crystal silicon thin film may be formed on an insulatingsubstrate and the film so formed may then be used to form the displayelement units.

In addition to the configuration of forming the display element unitsusing a thin film process on the insulating substrate, the displayelement units may also be formed on a silicon substrate.

In the above-described examples, the scanning circuit and the pixelsconnected thereto, are laid out in discrete locations in the plan viewshown in FIG. 3. These may also be overlapped together. For example, ifthe semi-transparent liquid crystal display device is formed using thepolysilicon process technique, the reflective region in the pixel isformed to be overlapped on the layout of the scanning circuit, while thetransparent region in the pixel is formed so as not to be overlapped onthe layout of the scanning circuit, whereby it is possible to derive theeffect of improving the aperture ratio and reflectivity.

In an EL display device, the fill factor may be improved by layout inwhich a light emitting part in a pixel is overlapped with t scanningcircuit in a plan view.

In the present example, a pixel switch is connected to an output of aDFF, and a sole sort of a data signal of each pixel switch is coupled tothe DATA node. It is however possible to connect three sub-pixels inparallel to a DFF output and three sorts of a data signal may beconnected to DATA nodes to make up a color display device. In moredetail, three sub-pixels 202 a, 202 b and 202 c are connected inparallel with an output node Q of a DFF, as shown in FIG. 8. These arered (R), green (G) and blue (B) pixels, to which are coupled independentdata indicated by DATA_R, DATA_G and DATA_B to implement a color displaydevice.

In the above-described example, a non-rectangular display area is formedon a display substrate of a non-rectangular shape substantially similarto the non-rectangular display area. It is however possible to form anon-rectangular display area on a rectangular-shaped display substrate.

For example, a circular-shaped display area is formed on arectangular-shaped display substrate, like the national flag of Japan.In this case, the four corners of the display substrate may be used as ascrew attachment area for connection of the display substrate to otherconstituent devices or elements. In similar manner, if a doughnut-shapeddisplay area is formed on a rectangular-shaped display substrate, thecenter opening area of the doughnut shape may be used as a screwattachment area. A specified example is now described.

Example 1

In the present example, a TFT substrate (Thin Film Transistor) substrateis prepared, using the polysilicon process technique, and an activematrix liquid crystal display device was fabricated using thissubstrate. The sell-known low-temperature polysilicon TFT-LCDfabrication technique was used as fabrication process. The detailedprocess for fabrication is stated in “Illustrated Low-Temperaturepoly-Si TFT-LCD Fabrication Process, 2005-issue, published by E-ExpressCo. Ltd.

Using the technique for low-temperature fabrication of polysiliconTFT-LCD, a TFT pixel switch of a planar configuration, a TFT of ascanning circuit and an electrode of the storage capacitor, wereprepared to form a TFT substrate.

The TFT that forms a circuit on a display substrate was prepared as aTFT of the same process. That is, the process is such as enables theoperation of a TFT in need of a high voltage.

A patterned pillar of 4 μm was prepared on this TFT substrate for use asa spacer for maintaining a cell gap and for assuring impact resistance.

A UV light curable sealant was coated outwardly of the display area of acounter substrate. The parts of the counter substrate not facing theaperture devoid of the pixels were provided with a light-shielding layer(so-called black matrix) to prohibit deterioration of the picturequality, otherwise caused by disclination. This also hides thenon-regular layout such as folded part of the wiring so that the pixelaperture part will be seen by a viewer of the display device as if thepixels in the aperture are arranged at an equal pitch.

After bonding the TFT substrate and the counter substrate together, acarbon dioxide laser of a wavelength of 10.6 μm, liable to be absorbedby glass, was applied to a cutting line for heating. A coolant wassprayed immediately to produce a crack. The resulting product waspressured and severed into plural pieces each having curved outer shape.At nematic liquid crystal added by a chiral material was injected asliquid crystal material. A twisted nematic (TN) was formed by matchingthe rubbing direction.

FIG. 9 shows the configuration of a circuit formed on the displaysubstrate. FIG. 9 depicts a detailed structure of the example shown inFIG. 2 in keeping with the layout. The display element unit includes atransistor that forms a DFF circuit in a rectangular location labeledDFF, and an inner DFF wiring laid out with the transistor. The displayelement unit also includes a pixel transistor, a pixel electrode and astorage capacitor, laid out together at a rectangular location labeledpixel. The display element unit further includes a clock (CLK), a firstpower supply wiring (VDD), a second power supply wiring (VSS), a Datawiring and a wiring for the storage capacitor (VCOM), laid out togetherfor extending in a transverse direction.

By arranging a number of display cells, thus laid out, in a transverselyextending array, the layout of a row of the display substrate wasprepared.

At the ends of the first and second rows, there were added wirings forconnecting the clock lines, first and second power supply lines, DATAlines and lines of the storage capacitors of the first and second rows,so that the display element units will be electrically connectedtogether in a unicursal fashion. The display area could be formed inkeeping with an optional outer shape by adjusting the number of thedisplay cells that make up the respective rows.

The display substrate, thus prepared, and a backlight, suited to theouter shape of the substrate, were combined together to constitute thedisplay device.

Since the display element units are arranged in a unicursal fashion, anoptional transverse size may be achieved by adjusting the number of thecells of the display element units that make up a row. Further, anoptional vertical size may be achieved by adjusting the number of rows.Hence, the display area matched to an optional outer shape may beachieved by adjusting the number of the display element unitsconstituting each row.

With the present example, in which the display element units arearranged in a unicursal fashion, all pixels are necessarily addressed.

Further, with the present example, in which all display element unitsare electrically connected together in a unicursal fashion, the drivercircuits, so far provided along the outer rim of the display substrate,may be dispensed with.

Further, with the present example, in which all display element unitsare electrically connected together in a unicursal fashion, the numberof connection terminals for connecting the display substrate and theouter circuit, may be reduced significantly.

The number of the connection terminals equal to the number of thetransverse rows of pixels, such as 100 connection terminals, as neededin the conventional system, may be reduced to only one in aconfiguration in which the DATA signal is provided from outside, thatis, a configuration on which a data driver is not provided on thesubstrate, as in the present example.

Since the TABs, so far provided along the outer rim of the displaysubstrate, may be dispensed with, the degree of freedom of the outer rimshape has been enhanced significantly. Or, since the driver circuit, sofar formed along the outer rim of the display substrate, may be omitted,the frame size may be reduced. Since the driver circuit, which was to beformed along the outer rim of the display substrate, may now beeliminated, it has become possible to marrow down the framewidth/length. The operation of laying out the driver circuit along, thenon-rectangular outer rim of the display substrate was extremelylabor-consuming, in the current CAD, but the operation may now bedispensed with, resulting in a shorter designing time.

In the present example, the DFF is made up of four clocked invertersCINV1 to CINV4, two inverters INV1 and INV2 and two inverters INV3 andINV4 for generating an inverted clock signal C1 and a non-inverted clocksignal C2, respectively, as shown in FIG. 10A. The configurations of theclocked inverter and the inverter are shown in FIGS. 10C and 10B,respectively. FIG. 10B depicts a CMOS inverter made up of a P-channeltransistor MP1 and an N-channel transistor MN1, connected between thepower supply VDD and the power supply VSS. The transistors of the CMOSinverter have gates connected in common to constitute an input node A,while having drains connected in common to constitute an output node Y.FIG. 10C depicts a clocked inverter made up of P-channel transistors MP2and MP1 and N-channel transistors MN1 and MN2, connected between thepower supply VDD and the power supply VSS. An input A is supplied to thecommon gates of the transistors MP1 and MN1, whilst an inverted clock C1and a non-inverted clock C2 are supplied to the gates of the transistorsMN2 and MP2.

FIG. 11A shows a modification in which the two inverters in the DFF forgenerating an inverted clock signal and a non-inverted clock signal areomitted and a clock signal and an inverted clock signal are suppliedover a bus. FIG. 11B depicts the configuration of the two-DFF circuitshown in FIG. 11A.

The clock signal and the inverted clock signal are supplied to CLK andXCLK of FIGS. 11A and 11B, respectively. In the present modification,the number of transistors needed for a pixel is 20 for the two-DFFcircuit and 1 for a pixel, totaling at 21.

In the present example, the excimer laser is used for forming apolysilicon film. However, other lasers, such as continuously oscillatedCW laser, may be used.

In the present example, a transmissive LCD is prepared. For producing asemi-transmissive pixel electrode, a transparent pixel electrode isinitially formed, a Mo film and an Al film are sequentially deposited onthe overall surface, and a photoresist pattern is then formed. The Alfilm and the Mo film are simultaneously patterned, and the photoresistpattern is then removed to provide the configuration ofsemi-transmitting pixel electrode, carrying the reflective electrode.

The transistors and the wirings, provided in the display element units,laid out on the display substrate, are laid out such that thetransistors and the wirings are overlapped with the reflectionelectrodes, when viewed in plan, while the transistors and the wiringsare arranged underneath the reflection electrodes, when viewed incross-section, thereby improving the aperture ratio of the pixels andthe area of reflection.

In the present example, the clock line, power supply line, data wiringand the wiring for the storage capacitors are arrayed unicursally.However, the unicursal array is not mandatory.

For example the data wirings may be arrayed vertically and thevertically arrayed pixels may then be connected, provided that thewirings are electrically connected together and connected to an inputterminal. However, at least the scanning circuit needs to be arrayedunicursally.

FIG. 12 shows an example of the circuit layout of the present invention.Referring to FIG. 12, a plurality of data wirings are arrayed verticallyand the vertically arrayed plural pixels are connected in common to thedata wiring. The data wirings are electrically connected together andconnected to the input terminal (DATA).

Since the course for drawing the clock line around differs from that fordrawing the data wirings around, attention has to be paid to signaltiming design. In more detail, the data signal timing is designed sothat data may be written in both the pixels lying remotest from andthose lying closest to the input terminal of the clock line (CLK).

In the present example, the clock signal is supplied over a clock lineto each DFF. A relay buffer may be provided halfway on the clock line inconsideration of the load capacitance of the clock line. In this case,the relay buffer is desirably provided at e.g., the folded part of thescanning circuit, that is, at an end of the display area, in order tokeep layout rules of the display area.

Example 2

In the case of the example 1 of FIGS. 11A and 11B, 21 transistors foreach pixel and a two-phase clock signal, namely a clock signal fordriving the scanning circuit and the inverted clock signal, arerequired.

The present example, which will now be described, has been devised bythe present inventor to reduce the number of the transistors and thenumber of the clock signals.

FIG. 13 shows the configuration of the scanning circuit and the pixelcircuit of the present example. In FIG. 13, a display device (200) ismade up of a circuit (206), forming a stage of the scanning circuit, anda scanning circuit (202), connected to an output node of the circuit(206). This circuit (206), forming a stage of the scanning circuit, ismade up of a sole inverter circuit and a sole switching transistor.Switching transistors 214 a and 214 c are of the n-type and switchingtransistors 214 b and 214 d are of the p-type. That is, the first-stageswitching transistor 214 a, second-stage switching transistor 214 b andthe third-stage switching transistor 214 c of the scanning circuit areof the n-type, p-type and of the n-type, respectively. The switchingtransistors of the odd stage are of the n-type, whereas the switchingtransistors of the even stage are of the p-type, respectively.

Output nodes n1, n2, n3, of the respective stages of the scanningcircuit are each connected to a pixel switch. The pixel switch,connected to the node 1, is of the p-type, that connected to the node n2is of the n-type and that connected to the node n3 is of the p-type, andso forth. That is, the pixel switches connected to the odd and the evenstages of the scanning circuit are of the p-tye and the n-type,respectively. Hence, the display device may be constituted by fourtransistors per pixel.

Also, the scanning circuit may be driven by a single-phase clock signal.Since the clock signal is a single-phase signal, and only one transistorsuffices to drive each stage of the scanning circuit, it is possible toreduce the load capacitance of the clock line and clock delay.

The operation of the scanning circuit and the pixel circuit, constructedas described above, will now be described. FIG. 14 depicts a timingdiagram for illustrating the operation of the present example. Referringto FIG. 14, an active-high pulse signal (one-shot pulse) of a pulsewidth of 2×T, T being a one-half period of the clock signal, is routed,as an input signal ST, to a terminal ST, at a rise timing from the lowlevel to the high level of the clock signal CLK, whereby a pulse signal,inverted from that at ST, is output at the node 1.

This signal becomes an input signal of a circuit forming a single stageof the scanning circuit constituting the next-stage display elementunit, such that a pulse signal is output, at a node n2, at a fallingtiming of the clock signal CLK, with a delay of T as from the signal atthe node n1.

During a period “a” attached to the pulse signal waveform at the noden1, the n-type transistor M01 is on, so that the node n1 is in a lowimpedance state. So, an inverted version of the pulse signal of thesignal received at ST is output at the node n1.

During a period “b”, the transistor M01 is off, and the node n1 is in ahigh impedance state, so that the voltage is retained by the capacitanceat the node n1.

Hence, an active-low pulse signal, with a pulse width of 2×T, is outputat the node n1.

During the period “a”, the p-type transistor M02 is off, and hence theimpedance is high. During the period “b”, the p-type transistor M02 ison, and hence the impedance is low, so that a high level signal,inverted from the input of the inverter INV02, is output at the node 2.

During the period “e”, the transistor M02 is off, and the node 2 is in ahigh impedance state. The voltage is retained by the capacitance at thenode n2. Thus, an active high pulse signal of the pulse width 2×T isoutput at the node n2.

In this manner, an active-low pulse and an active-high pulse aresequentially output at nodes n3, n4, respectively, each with delay ofthe pulse period T.

In this manner, active-low pulses may be generated at odd-stage outputsof the scanning circuit at the nodes n1, n3, n5, whilst active-highpulses may be generated at its even-stage outputs at the nodes n2, n4,n6, . . . .

Referring to FIG. 13, the polarities of the pixel switches are set sothat the pixel switches will be turned on by these polarities of thescanning pulses. That is, a p-type transistor is provided at each pixelswitch connected to an odd stage output of the scanning circuit, whereasan n-type transistor is provided at each pixel switch connected to itseven stage. Thus, the pixel switch, connected to the node n1, is onduring a sequence of periods “a” and “b”.

During the “on” periods of the pixel switch, the capacitance of theliquid crystal cell and that at the storage capacitor ischarged/discharged in keeping with the voltage signal of the data signalDATA to determine the voltage written in the pixel at the off-timing ofthe pixel switch.

Hence, the voltage signal, written in the pixel, connected to the noden1, becomes equal to D1 written in the DATA node at the rise timing ofthe node n1.

Similarly, the voltage written in the pixel, connected to the node n2,becomes the voltage signal D2 applied to the DATA node at the fallingtiming at the node n2. In this manner, the voltage to be written in thepixel is sequentially applied, at each period T, to the DATA node.

The scanning circuit sequentially addresses the pixels, beginning fromthe pixel connected to its initial stage, up to the pixel connected toits trailing stage, thereby writing data for one frame in these pixels.

The pixel circuit connected to the even stage of the scanning circuitdiffers in circuit configuration from the pixel circuit connected to itsodd stage, with the result that the corresponding difference is producedin the display characteristic. To keep up the picture quality as adisplay device, the pixel circuits need to be ingenuously laid out sothat different pixel circuits will be arrayed in both the horizontal andvertical directions.

The circuit of the present example was formed on a glass substrate, anda display device was implemented with the use of a driving system inwhich the polarity of the common electrode is reversed. The voltageapplied to the liquid crystal was set in a range from 0V to 5V, so thatsufficient contrast will be achieved. One of the voltages, in case ofreversion of the polarity of the common electrode, was set to 0V, whilethe other voltage was set to 5V. Since the voltage at the pixelelectrodes ranges from −5V to 10V, in this case, a voltage less than −5Vand a voltage higher than 7V are needed to turn the pixel switch off andon, respectively, in case the pixel switch is of the n-type.

When the pixel switch is of the p-type, a voltage higher than 10V and avoltage less than are needed to turn the pixel switch off and on,respectively. For this, the voltage range needed at the output stage isfrom −5V or less and up to more than 10V or higher. To enable this, thepower supply voltages of the inverter were set to −5V and 10V. Totransfer the voltage signals of these amplitudes by the switches M01 toM04, the clock signal voltage was set to −7V and 12V. These may besummarized as follows:

That is, in the present example, the voltage of the DATA signal rangesbetween 0V and 5V, the power supply voltages for the inverter are −5Vand 10V and the low and high levels of the clock signal are and 12V,respectively.

With the above circuit, four transistors suffice per pixel, while asingle phase clock signal suffices for driving the scanning circuit.

That is, if the present circuit is compared to FIG. 11 of the example 1,the area taken up by the transistors or line per pixel, reduced, thusimproving the aperture ratio or the resolution of a transmissive liquidcrystal display device.

In the present example, the scanning circuit is of the dynamic circuitconfiguration. However, the circuit configuration may be modified to astatic configuration by suitably adding feedback circuits. Although FIG.13 shows a configuration in which a number of display, element units(200), each made up of the circuit (206) and the circuit (202), forminga stage of the scanning circuit, are stringed in a row, theconfiguration may be branched, if so desired.

Example 3

An example 3 of the present invention will now be described. Referringto FIGS. 15A and 15B, the scanning circuit (204) of the present exampleincludes a clocked inverter (56) per stage of the scanning circuit.

A sole pixel switch (350) is connected to output nodes n1, n2, n3, . . .of the circuit (206) that constitutes a stage of the scanning circuit.The pixel switch, connected to the output node 1, is of the p-type, thatconnected to the output node n2 is of the n-type and that connected tothe output node n3 is of the p-type, and so forth. That is, the pixelswitches connected to the odd and the even stages of the scanningcircuit are of the p-type and the n-type, respectively.

Thus, a display device may be implemented using five transistors perpixel. The clock signal that drives the scanning circuit is CLK and itsinversion XCLK.

The operation of the scanning circuit and the pixel circuit, constructedas described above, is now described. FIG. 16 depicts a timing diagramfor illustrating the operation of the present example. Referring to FIG.16, an active-high pulse signal of a pulse width 2×T, being a one-halfperiod of the clock signal, is routed, as an input sign al ST, at a risetiming from the low level to the high level of the clock signal CLK,whereby a pulse signal inverted from that at ST is output at the node 1.This signal becomes an input signal of a circuit (206) forming a singlestage of the scanning circuit constituting the next-stage displayelement unit, such that a pulse signal is output, at a node n2, at afalling timing of the clock signal with a delay of T as from the signalat the output node n1.

During a period “a” attached to the pulse signal waveform at the noden1, the output node of a clocked inverter CINV01 is in a low impedancestate, so that the node n1 is in a low impedance state. So, an invertedversion of the pulse signal, received at ST, is output at the outputnode n1.

During a period “b”, CLK is low and the output node n1 is in a highimpedance state. The voltage is retained at a capacitor of the outputnode n1. Thus, an active-low pulse signal of the pulse width 2×T isoutput at the node n1.

The output node n2 is in a high impedance state during the period “a”,and is in a low impedance state, during the period “b”, to output a highlevel signal which is an inverted version of an input signal of theinverter CINV02. During the period “c”, the output node n2 is in a highimpedance state to retain the voltage by the capacitance at the outputnode n2. Thus, the output node n2 outputs an active-high puke signal ofthe pulse width 2×T.

In this manner, the output nodes n3 and n4 output active-low andactive-high pulses, respectively, with delay of time T.

In this manner, odd-stage outputs of the scanning circuit, i.e., theoutput nodes n1, n3, n5, . . . may generate active-low scanning pulsesignals, whereas even-stage outputs of the scanning circuit, i.e., theoutput nodes n2, n4, n6, . . . may generate active-low scanning pulsesignals.

Referring to FIGS. 15A and 15B, the polarities of the pixel switches areset so that the pixel switches will be turned on with the scanning pulsesignal of the polarity shown, in the same manner as described withreference to FIG. 13.

Hence, the voltage signal, written in the pixel, connected to the outputnode n1, is D1 applied to the DATA node at the rise timing at the outputnode n1.

Similarly, the voltage written in the pixel, connected to the outputnode n2, is the voltage signal D2 applied to the DATA node at thefalling timing at the output node n2.

In this manner, the voltages to be written in the respective pixels aresequentially applied to the DATA node at the period T.

In the present example, in contradistinction from the previous example,the low level voltage and the high level voltage of the clock signal arethe same as those of the power supply voltages of the clocked inverter.Thus, in the present example, the number of the sorts of the powersupply voltages to be provided for driving the display device as well asthe voltages to be applied to the transistors may be reduced toadvantage.

With the above-described circuit, five transistors are needed per pixel,while two phases of the clock signal are needed for driving the scanningcircuit. The amplitude of the voltage of the clock signal may be thesame as that of the power supply voltage of the clocked inverter.

In the present example, the circuit configuration is the dynamicconfiguration. However, the circuit configuration may be changed to thestatic configuration by adding feedback circuits if so desired.

In the present example, the configuration made up of an inverter 54 anda transmission gate 58 may be used in place of the clocked inverter, asshown in FIG. 15B. The operation and the feature of the circuit of FIG.15B is the same as those of the circuit employing the clocked inverter.

Example 4

In the present example 4, the number of the transistors is five, theclock signal is the single-phase clock signal, and the amplitude of thevoltage of the clock signal is the same as that of the power supplyvoltage. FIGS. 17A to 17C shows the configuration of the example 4 ofthe present invention. Referring to FIG. 17A, the display circuitincludes a circuit (206), forming a single stage of the scanningcircuit, and a pixel circuit (202), having an output signal of asingle-phase clock controlled inverter (60) as an input.

FIG. 17B shows the circuit configuration of the single-phase clockcontrolled inverter (60) shown in FIG. 17A. Referring to FIG. 17A, twoP-type MOS transistors M01 and M02 and two n-type MOS transistors M03and M04 are connected in cascade, between a power supply VDD and theground potential VSS. An input signal is supplied to the gates of thetransistors M02 and M03. An output signal is taken from the connectionof the drains of the transistors M02 and M03. A clock signal is suppliedto each of the transistors M01 and M04.

The operation of the single-clock controlled inverter is now describedwith reference to a truth table shown in FIG. 17C.

When the clock signal is at a high level, the p-type MOS transistor M01,the source electrode of which is connected to the power supply voltageVDD, is off, while the n type MOS transistor M04, having a sourceelectrode grounded, is on. If the input signal is high in level at thistime, the output signal of the jingle-phase clock controlled inverter(60) is low in level, whereas, if the input signal is low in level, theoutput signal is high in impedance:

If conversely the clock signal is at a low level, the p-type MOStransistor M01, the source electrode of which is connected to the powersupply voltage VDD, is on, while the n type MOS transistor M04, having asource electrode grounded, is on. If the input signal is high in levelat this time, the output signal of the single-phase clock controlledinverter is high in impedance, whereas, if the input signal is low inlevel, the output is high in level.

The operation of the display circuit of the present example is nowdescribed with reference to FIG. 18 showing a timing chart forillustration.

A pulse signal of a pulse width 3×T, T being a one-half period of theclock signal, is supplied, as an input signal, at a falling timing fromthe high level to the low level of the clock signal CLK, whereby aninverted pulse signal is output at the node n1 at the falling timing ofthe clock signal CLK.

This signal becomes an input signal of the next stage single-phase clockcontrolled inverter, such that a pulse signal is output, at a node n2,at a falling timing of the clock signal CLK, with a delay of a period Tas from the signal at the output node n1.

During the periods “b” and “c”, attached to the pulse signal waveform atthe node n1, the output of the single-phase clock controlled inverterCINV01 is in a high impedance state. However, the voltage during theperiod “a” is retained by the capacitance at the node n1.

Thus, by the single-phase clock output CLK, an active-low scanning pulsesignal may be generated at outputs of the odd-numbered stages of thenodes n1, n3, n5, . . . , whilst an active-high scanning pulse signalmay be generated at the outputs of the even-numbered stages of the nodesn2, n4, n6, . . . in the scanning circuit.

Referring to FIGS. 17A to 17C, the polarities of the pixel switches areset so that the pixel switches will be turned on with the scanningpulses of the polarities shown.

The voltage signal, written in the pixel, connected to the node n1,becomes D1, applied to the DATA node, at the rise timing at the node n1.

Similarly, the voltage signal, written in the pixel, connected to thenode n2, becomes D2, applied to the DATA node, at the falling timing atthe node n2.

In this manner, voltages to be written in the respective pixels aresequentially routed to the DATA nodes, at intervals of a period T. Sincethe clock signal is again of a single-phase in the present example, thecapacitance of the clock line is small and the clock delay is alsosmall.

Other Example

In the above example, description has been centered about the liquidcrystal display formed using the polysilicon process technique. However,the present invention may also be applied to an organic EL displaydevice, the scanning circuit and the pixel circuit of which are formedof polysilicon.

In the above example, an instance in which the scanning circuit and thepixel circuit are formed by a thin-film process on a glass substrate hasbeen described. However, the present invention may similarly be appliedto a display device in which the scanning circuit and the pixel circuitare formed on other insulating substrates or a silicon substrate.

In the above example, planar display on a glass substrate has beendescribed. Alternatively, a flexible display device may also be formedby peeling off a scanning circuit or a pixel circuit, prepared using thepolysilicon process, from a glass substrate, and by transcribing thecircuits on a flexible substrate. The so formed flexible display devicemay then be processed to produce a display device presenting a curvedsurface.

The scanning circuit and the pixel circuits, connected to respectiveoutput nodes of the scanning circuit, may be formed on an elongatedflexible substrate which is then wrapped around a support to form aplanar display surface.

The present invention may be applied to advantage for a mobileelectronic device, such as mobile phone terminal or mobile media player.Since a display device of an optional outer shape, taking up a largevolume or space, may be provided as a component part of the mobileelectronic device, the degree of freedom in designing the electronicdevice may be improved, as a result of which a mobile electronic devicewith improved fashionability may be produced.

Among examples of use of the present invention, there are variable sortsof small-sized electronic equipment, such as an electronic still cameraor a video camera. With this sort of the electronic equipment, it isbecoming difficult to procure a sufficient and compact space in which toinstall a display panel on the electronic device. With the use of thedisplay device of the present invention, a display panel may be arrangedby exploiting spaces of variable shapes.

Among other examples of use of the present invention, there are variousaccessories, such as pendants, timepieces or buttons. Through the use ofthe present invention, the display device can be installed on theseaccessories. By so doing, design features of these accessories may behighlighted to meet the user's taste to help increase the sale.

Among further examples of use of the present invention, there arevarious meters mounted on a bicycle or a car. With the use of thedisplay device of the narrow frame size and the optional outer shape,characteristic of the present invention, it is possible to fabricate themeters with the smallest possible mounting space. The field of view,otherwise interrupted by these meters, may be diminished to improve thesafety.

Among further examples of use of the present invention, there aredisplay devices installed on commodity demonstration racks or shelvesfor sale promotion. A display device of a fantastic design will attractthe customers' attention to improve the ad effect. Since the total areaof the display device of an optional outer shape may be used as adisplay area, the proportion of the space taken up by the display deviceof an arbitrary shape to that taken up by commodities, placed on theshelves at the back side of the display device, may be reduced.

Among further examples of use of the present invention, there arevariable sorts of amusement equipment, such as pachinko table. Forexample, if a tulip-shaped display device is prepared through use of thepresent invention and mounted on a tulip base of the conventionalpachinko table, the pachinko table will appear more luxurious to helppromote the sale of the pachinko shop.

Among still further examples of use of the present invention, there arering-shaped accessories or ornaments, such as rings or bracelets. Inthese, hitherto unprecedented design features may be produced to helppromote the sale. As described above, in the display device according tothe present invention, a plurality of pixel circuits are able to beprovided with plural items of data, respectively, and hence any image,such as a character or logo, still image and moving image can displayed.

Although the present invention has so far been described with referenceto preferred examples, the present invention is not to be restricted tothe examples. It is to be appreciated that those skilled in the art canchange or modify the examples without departing from the scope andspirit of the invention.

It should be noted that other objects, features and aspects of thepresent invention will become apparent in the entire disclosure and thatmodifications may be done without departing the gist and scope of thepresent invention as disclosed herein and claimed as appended herewith.

Also it should be noted that any combination of the disclosed and/orclaimed elements, matters and/or items may fall under the modificationsaforementioned.

The invention claimed is:
 1. A display device comprising: a plurality ofstages of unit circuits arranged in a cascade connection to form ascanning circuit, each of the unit circuits including an input node toreceive a scanning signal, a clock input node to receive a clock signaland an output node to output the scanning signal, each of the unitcircuits, responsive to the clock signal received at the clock inputnode, outputting from the output node thereof, the scanning signalreceived at a scanning signal input terminal or received at the inputnode thereof from a preceding unit circuit to transfer the scanningsignal to a succeeding unit circuit from the output node thereof andsupplying the scanning signal from the output node thereof to a pixelcircuit arranged in a stage corresponding to each of the unit circuits;a plurality of the pixel circuits, each of the pixel circuits including:a display element having a first end connected to a common electrode;and a switch transistor adapted to be turned on and off by the scanningsignal supplied thereto from the output node of a corresponding stage ofthe unit circuit, the switch transistor arranged between a terminal towhich a data signal is supplied and a second end of the display element;and a wiring that is connected in common to terminals to which aplurality of the data signals are applied, wherein a voltage signalcorresponding to an grayscale level to be displayed by the displayelement is sequentially applied to the wiring with a clock cycle,wherein a plurality of the display elements are arranged in atwo-dimensional directions to form a display area, with the scanningcircuit disposed inside the display area, as viewed in a planer view,wherein the scanning circuit and the pixel circuits are formed on anon-rectangular substrate with one or more edges being curved, as viewedin a planer view, and the display area, inside of which the scanningcircuit is formed, is formed along the edge of the substrate, whereinwith respect to a row of an array of the display elements, a part of thescanning circuit is disposed between two adjacent rows of the displayelements.
 2. An electronic device including the display device as setforth in claim 1.